Radio transmission system



Nov. 9, 1.943.

H. w. KLrNE 2,334,011

RADIO TRANSMISS ION SYSTEM Filed Feb. 21, 1941 2 sheets-sheet 1 CAR/PIER TRANSMITTER byJVa/vfyf HIS Attorney.

Nov. 9, 1943. H. w. KLINE 2,334,011

RADIO TRANSMISSION SYSTEM Filed Feb. 21, 1941 2 Sheets-Sheet 2 wa/0 ,4Min /F/fn fm" GENERATOR Inventor: HaseyW. Kline, b ymy J Hi s Attorney.

l"c listance.

Patented Nov. 9, 1943 anni UNITED STATES PATENT- -fo'rfrlcs 2,334,011 RADIO TRANslmss'io sifsTEi/i Halsey W. Kline, Schenectaldy,YN. Y., assigner to General EiectricCompany, a corporation of New York Application February 21, 194i;

14 Glaim's.

"This invention relates to a signal transmission system, and more particularly to a carrier Wave systemior transmitting signals in lWhich fading 4is` minimized or eliminated.

. In theart'of radio communication it is Well known that a radio Wave of medium or high frequency often cannot be received' Within a zone which may', for example, lie (for a 20 meter wave). between 50 and 700 miles from the! trans.- mitter. In other Words, kunder arcertai'n's'et 'of conditions, the' Wave may, for examplebere- V,ceive'd only within 50"m'i1es of the transmitter, or

farther than 700 miles from it -The Width of `such yazone in Which the transmitted wave cannot be received is commonly termed the skip Y distance. Itv isusuallyassumed that this skip exists because' a radio Wave from a transmitter z noves near the ground only for a short distance before it becomes attenuated to an intensityftoo flow VtolteV received, while ionized'v layers in the upper atmosphere reflect theV waveV from the transmitter. to positions much farther removed than those to which the ground Wave reaches.

K yVarying reilection from. the ionized layers pro--y "duces fading. l

it is an object ofimy invention toprovide an improved signal transmission system hy which ycomin;inication may be carried on at distances from the' transmitter'within the normal skip ',It is also anpbject of my invention to'pi'vide an limprovedsig'nal transmission system inwhi'ch fading effects are minimized.

To attain these objects I utilizeV a system' in Awhich a' radioL Wave, for example, is radiated in sucha way that a directional characteristic may `be changed. VIi the' radiation is in theior'mv of `a"beam, the direction of propagation of the' beam 'maybe alteredperiodically. Asthe beanidiffer:L tion is periodically altered, reection from Athe 'ionizedlayers varies in direction and position,

so that-many points not reached by al Wave-propagated in' a single direction are reached intermittently by suchradiation `Whose direction ofprop- Wave may:v be' radiatedand the directie-nl of p'- larizatiorr4 altered intermittently to v produce Y sirnilaif results. f

z when eitiieimr these'direetionai Characteristics altered; the r'intensity ofradiationispreierablykept'l constant,.whereby fading is reducedfa't .'distantpoints to which such radiation isireected `from upper strata' of` the atmosphere;- in' par- ,ticeiilanseective'fadng;A due to lunequal transmission of 'sidegbandfsfis lessened.A f

ramasser/e1' 1 kveimoii to' provide' en im" 'sig j' fine" features'or in tages thereof may' best be understood b 'a receiver' fsr' ifs-centri 'connected thc'iiiglf a conductor i6 to the to'be novel reset f appended' claims.'

the' fair win' miner munir ten" e, s forfnjf my invention In igf l tietrsfiiitter i cuity f, which is' maintained i, electrn discharge device 4I l oscillations" areA ampliii carrierv transr'iitti" ll ed circui4 slun-te'dly'a resistA trode li'roi'the dev devicell is cornectedtr of theme-ed c iit mi; 'rm-anode M is'jediinegerinneneessa e1n-entere; @Lf Operatinsoteniials The img; 011101.11@ i?? and cicopan-ying elem-entsthus form a usual type Oufipm'ton f 1;; ,Iy

Thedipole antenna i3 ,liesf ara el to the fabel of the ser-th and-a1; :.asdlsienel @bore-:tbe surface of the eartlrequal toI onequarterwave ,lengthpf the waveiinpressed vonthe antennaJl A Similar; dirmi@ antenna A2,3.- is piaced parallel l t5 from Athe antenna l3and one-guarterwave length abovetlfie vsurface oi the-earth -If'he dipole an: term@Y 213 is interrupted @brits *Der` @i the-ineffupiien'iS-bidged seessfre'su., n.tlgfcuii comprising an inductane; @j condenserZ wenn; electron dwellers@ devise 21%;y lhe dipolefantenna 23:15 arrangedl t0 ad'. este reflector of the waves radiated fr camtlie antenna I3. This reflecting antenna 23; by a.,djustment,'`

waves of a particular frequency.` When theresonant frequency of the series resonant circuit is phase, with respect 'to the'voltage betweexrtllel y made equalto the .frequency of,;Waves ra'd-iated from th'e antenna |3,fthe antenna' 23 is, in -effect, connected together rat its` center so as to act most effectively asa reflector forwaves'from Y..

the antenna I3. Whenso adjusted the antenna., e

'f l'through'the device 26 may be adjusted by chang-` system acts to radiate ywaves in a direction'sub= stantially opposite to the direction of theanterma.;

23 from the antenna I3.

When thefresonant frequency of the series res;

onant circuit is adjusted to a'frequencydiierent from'that of the waves radiated kfrom 4the. an;

anode 21 and cathode 33, is developed across the resistance 39, and applied to the control electrode 3y. Alternating current which ows through the device 28 is'in phase with the leading alternating v potential on the control electrodes 33e. Any a1- ternating potential which exists between the antherefore,l 'accompanied Qbya lleading alternating current, so that the `device 2S simulates a condenser. y

,'The amount of Aleading current which flows-- ing'the potential across the resistance 39, there- .b'y'fchangingj the'. apparent reactance oi the device 26 invits actionin simulating a condenser.- As

- thev apparent -reactance' of the device 26 changes.

' the resonant'frequency of the series resonant tenna |3,.the reflecting antenna 23 is effectivelyv interrupted at its center,y and does not 'reflect waves of such' frequency. When so'adjusted; the antenna system radiates waves-upward from the antenna I,3,'because of 'the reflecting'fpower of the surface of th'eearth. Therefore by a'dju'stf ment of the resonant 'frequency Vof thes'eriesre's'- onant circuitconiprising' theinduc'tance 24,`th e' condenser 25, and the discharge devicza] the direction, 'in a Verticalv plane,'f in which' Waves The electron'discharge device "2S, which isa part of the series resonant circuit'isfsdconnect ed in shunt' to the condenser`25 as toitransmitrphase of voltage acrossv c'ondenser'l'by afsubstantial angle 'and whichV therefore, simulates a condenser connected in 'shuntto condenser 25: The anode 2 1 of the device 26 isconn'ectedto'a point between theinductance 24j and one terminal o f the condenser 25, and the cathode 331s connected through aresistance' 3|:y inr shuntv to a bypassing condenser 32, and `a'cc' n ductor 14|to "the other terminalof thev condenser 25.` The'devicef" 23 is supplied'` with operating current minalis 'groundedja choke coil 30, and :theyresistance 3|v to the cathode` 33v ofthe device 26.

The screen electrode "34 is supplied withfoperating potential through a resistance 35 from the positive yterminalv oi source 29;and isfbypa'ssed through'a bypassing condenser "36 toapointl between the choke coil 30 and-the resistance Av potential is'supplied from the anode of d'e- Y circuit" including inductance 24, condenser` 2i, and discharge vdevice V26,1. changes With .aconcur- 'rent change in the, `directionloi: 'maximum radintionlfro'rn kthe antenna'. I3.

j Audio `signals from Ya microphone 4'2"'arej fled rin amplifier 4.3and applie'dacrossfthrrefsisian'ce asse as to change'tnemrectionlor maximum radiation iromthe antenna 'I3 in' accord? betransmitted. y'i'he output cirjcuit 'o'fiamplier 43 includes 'a switch '41'. having ,three positions Stance 'ItS' :operation L when. 1 1 the' other 6r its positions Wm-later be mmcatgd. i, i t

j rhetransmittergas unis jqesribedjmay justedin several'ways.Y Th source-1015 pogen.

tialmay be madejust'ilarge enoughto make the apparent reactance off'the device 26, in the ab-y sence'of a signa/renom' the 'microphone 42,1101' `proper value tofmake the series resonant circuit,

includinginductance 2 4,"`condenser25, and dig.. chargc'devce 26; resonate'at the `frequencywof waves from the" antenna.. |3.'j The outputjof'the anni() amplifier @la mythen bepled in either Pdirection, 'so that 'thej apparent 'reactance of they of reactance in eithef ronant", ireoluer'icy off'the series resonant circuit,

vice 2B throughl condenser to the control elecl trode 38 in such phase with respectto valter/nating potential between the anode 21 and the'cath'- odej 33 as lto cause alternating current to'iow through the anode and cathode having a@ sub'- stantially leading phase relationto the alternating'voltage therebetween.V This alternating Vvpotential-is impressedvonthe controlg'electrode 38 through av network comprising Y condenser' 31- and a resistance 39 and a source 40 lof potential connectedl in series between the control electrode 38 and a point'betweenfthe` choke coil '30 and the resistance 3|. AThe source 40 maintains `ra, suit- 'ablefbias potential `for the'control electrode 38. Y

Alternating "potential between the lamide-21 nd'the cathode33is impressed across theseries combination of condenser v:i1- and resista-nce 39,' whereby alternating vcurrentv ofv leadingphase Aflowsl through the condenser and resistance.

-Gonsequently, an alternatingvoltage offleadin'g and reduces -the 'eiiectivene'ssjfof thel 23 as a reflector, vso that the direction. o! radiation v'tensityoi the audio signal.

of the waves'is changed 11iL responsei-.qtnefm- `A 1temame1y the 'potenciar lsource 4l may befrna'de oLJsuch yvalue as .to make Ithe series. .resonant circuit resonant lat aA frequency-removed fromthe. frequency" waves furomthe I3 by an amount` equ`al .to.the shift otresonant-he- A quencycausedby theaverage-fpealcintensityof I t6 `signals"from theL microphone 42.. .'Suli signalent peak` intensity then make the series eircuitresonate'atf'the freduencyof waves fromantenna I3, I@ .y f

Eorthe reception offwaves suchla transmitter an ordinaryrreoeiver f for thereception of amplitude modulated m is suitable.v Althoughthe frequency tude of the wave radiated from the .aiimna Il are .constant at all times, the. Intlmtifui'trans- .mission which comprises varying the y.of propagation of4 theV rradiationz.causes the .dilltantgfreceiver to rreceive more or energy in accordance with thalintensityfog signal :from the -microphonef-Theli'reoswed waveA therefore appears-to in* vnal be higher than the highest frequency of the `dinary typereceives` the carri .tently, as l explained in connec ble. An ordinaryreceiver,

n rierpwav'e with nomodulation.

' transm sition. An antenna I the carrier wave as it P,9S Se -With' the fblades ofthe switch 41 in the abQve mentionedjdownward position,l the `blade :45j is l connectedto ground, and the blade 45 is';con nected through a conductor |06 and a resistance |01 tothe control electrodegl03. Amplified signals from the microphone l2,therefore; appear acrossezthe resistance |05, change the amount of leading current passingthrough the discharge" device 80, ychangethe frequency of the, continuvousioscillations maintained inthe tuned vcircuit 82,83, change the Vfrequency at Vwhich thefamount of leading current passing through .the-device 26 is changed, and consequentlychangey the frequency at which the beam lof, radiation froml the l antenna I3 is swept upand^ down in ayvertical plane in response tother intensity of the signals from themicrophonezll... r r A 1 t It is preferred that the ratefa't which the beam is swept up and down in the ,absenceof` a sigsignal whichit is desired to transmit. For example, if it ybe desired to transmit an audio' signal Q havingr frequenciesextending, for.I example, y to 10,000 cycles, itis preferredthat the discharge device 8| produce oscillations havingl a frequency higher than'10,000 cycles, for example, ofjuthe order ofA 20,000 to 50,0 00cycles An ordinary receiver desi Y ed to VVdetect waves modulated in accordance with signalsof less than 10,000 cycles, cannot respond to such ',atrans'- mitted wave. `As` explained before, the amp/litude and frequencyhofa.transmitted wavefarey y constant vat alltimes, Vthedirectionof transmis,- sion being varied. i A ,distant receiver 'of the` jorer wave intermittion wahpncgz, such a high rate ofAspeed as to be inauditherefore, receives the transmitted wave as-a continuously-radiated carbut at InKFig. 3. there is illustrated aspecial receiver which I 'have provided forreception of thewlave itted by the transmitter illustrated` .in h 4.1 iS in itsy dcwmwerfl"V PQ- I0 is f. arranged to` receive gg S the ,reciveoriad t0 impress it upon areceiverV I II, which Acomprises asuitble tuning and amplifyingapparatus f0.1 the carrier wave. ri'he output ofthe receive1- l ;I,I is supplied through a transformer I I2, tuned by 25,0 a. condenser I I3 to the frequency of V:the lcarrier swan a wave, upon a diode detectorwl Il Vin serie 'Passing load 1 when thee switc load resistance II5., A high frequency, by condenser VI I6 is connected 4.in shunt Ato, `th resistance I I5. Y

When the beam s radiated .from ,the ktraliemitter in such a direction as to produce maximum .energy at the receiver, a voltage Vis ,produced across the resistanceA I YI5 in accordance Awiighthe maximum intensity of the carrier wavea'c ther/go receiver. vWhen lthe beam is radiatedfrom (the transmitter in other` directions such. thatfminimum energy is received atr the receiver,la' mini' mum voltage appearsacross theresistance IIV5. The voltage across the resistance -I I5, therefore, Avg5 corresponds to the output -voltagenof the tuned l circuit 82, 83, The frequencyof theyoltage f acrossv t-he Vresistance I I54 is, therefore, constant" Y inthe'absence ofv asignal from the microphone l2, Aandvaries in req'uencyefrom this constantw'm frequency when asignal n is transmitted from` the microphone 42. The voltage-,across'tlie resistance` -I I5, therefore., has they characteristics; .ofyaz frequency' modulated carrier wave, 4except that frequency maybe lower than'eradio the average '15 j treouexieles.'`

,15 .voltage ac3 20 amiamo the f Avoltage is. all

Y@wenige @weeen-m991931- mately the predetermined frequ, yr gat-which the tunedercmtrL- Operates ,11.1 ,the 0i sienaifromthe'microehene 42. and,y as

above.` may be of the-order 993013129 ,t0 .50:510-

A di ereetifier.. -il of .Potentiale-@www1 .in sries. elle ymehr: reconoce'.'nieuwe as "umerrm Pete @einem source. llriserhall. #ridge-SM1? diodefnqeandetivfhi the" absence Wwe .acrossetheresumed! A,

ess. resistance; H51 has., a" value `atEallivialluesr 'f Volta'gejacross 'theresistance |15 greater than vthe 'pote'nti'aliofl the j source II I 8," the signal'voltage whiohfcariiappe'a'r diode V.I I1 Varid the'source IIBin series-isiliinited to a ,30 Vco'r,istanti 'maximum value.: E"

,ilsywhichcircua 'is'amimgedA to wwe 'deviation of? the frequency of the voltage across Vandj magnitude correspond 'toj the amount f 1' such' deviation. ,"This voltage'represents' the signalsfrom the microphonel or the.

frequency fof the l`continuous oscillations main- Itained in thetuned circuit 82, when .no signal from'jthe microphone 42'.

circuitwhichzis'o'poected 4 resistance -I`I5comprises apair 'of diode recti-Y `r ners |22 ja'nd 123, 't "leach of whigchtwo'components of voltage" areiapplied'." Onecompoent'of n plied toeachof thefdiode'rrectifiers |22 'iand" l,23,vwhich component is inpha'se'with voltage 'across ith'e 're'sistanoe I I5; jThdSelatf Y,ter components; are ,applied throughvja coupling l gconjclcaser,4 lz connected, betweeo'thecenter tap of "a vtra'.'n`sioreiner A'I' ISjand a 'point between1 resinjanoe "i I 5' and detector Ijl dqTo the secondaryfof this; transforn'ierfly It the diode `rectifiers vI'22l and I2 3 "are i connected` in, opposing* relation through fa balanced load 'circuit comprising aY pair of seirries 'j'connected rloadresistances infini-125.9 A bypassing condenser IZBis connected in shunt' to `the twojload resistances 'and a second VYcondenser r|21 isconnected ini-shunt-fto'the'lood Y resistance 125. `Tiiesretwo" bypassmgcondensers )have l'ow' impedance to .voltages 'ofi te'frcqency ,ofthe ,voltage across tneresistanceni5,1m sub'- .Lst'antial 'impedance' at the-highest frequency -oi' Zsignal 'voitagesfrom the microphone n@ 'The l,circuit 'is arranged' so that the aboveedvescibed two components, applied tothe respective-jdiode recnnersf z2 and |23,` produce andV- opposite voltages 'across the respective two |25 'cod Iza., A: conductor 13| is v tween thev center'tap'of the secondatyof trans@- fouinerns 'anais point bepweenme ioadfrecistg once ne and-m;

ff lsecond ,componen 'or detector; "flee/falsare s sg ii when thefaltefoaang "i gr aterk than`the 'voltage ,of source -I"I$ there is ins/nuota: the

I 22,.and |23. Thissecondcomponent is applied through thetransformeraction ofthe trans- .former IIS, whose primary is connected in shunt to resistance 5V and whose secondary, shunted by a condenser. |22 forms ay tuned circuit. If

the. frequencyofA thevoltage 'across/resistance I5 ris the same as the resonant frequency ofthe tuned circuit, including the condenser 2l! and the trans,- iormer ||9,`. the transformer ||9 impresses -a voltageon one of the diode rectifiers, which Voltage leads Lby substantially 90 the voltage across the resistance I I5. The,tuned transformer applies across the other diode rectifier a voltage of equal magnitude, which voltagelags-by substantially 90,y the voltage across the resistance I5.

thefrequencyof the voltage across, the resistance I|5 changes, this phase relation between the various components changes,so that the ,two components across one diode rectier are ypears across one of th'egload resistances, maand l25lthanacross the other, and a net signal volt,- age 'is therefore"h present across ,the series combii nationof lthe two loadA resistances` The signal voltage across the resistances |24 .and |25 is transmitted through a coupling condenser `|28 to the Yinput of anaudo amplier |22,

.which amplies the signal and transmits it to loud speaker |30.

.ey furtheradjustment 'of mesme-Cn time y* Y transmitter illustrated in Fig. l may be utilized for a third type of transmission in which the b eamfrom the antenna |3 is swept up anddown in a verticalpl'ane at a constantV rate, while the frequency of the carrier wave is modulated Ain response toA the intensity of a signal. In this third connection of the transmitter, continuous I variationof the direction of transmission of radiationfrom the antenna I3 assures reception at the distant receiver, as 'explained above in c'o'nnection with Fig.='2, while modulation of the fre'- quency of the carrier wave in response to theinltensity of ani audio signal provides signal transc mission witl'iout selective fading associated with multi-path transmission, such as occurs' with an amplitude modulatedwave.

i Such a reconnection-of the transmitter may be y eiectedbyf moving the blades of the switch 41 to theupper zposition, inwhic'h' audio signals from theimicrophone'lM-'are c'aused'to vary4 theYfre-i quencyof oscillations in the. tuned vcircuit Ill in response tov 'the' intensity ofthe signals. `With across thef resistance IBB', with Y the result vthat e a=constantcur-rentows throughV the anode'and 'this :'reconnection, no" 'signal' voltage isv applied is interconnected with the. tuned circuit I0 in the saine way asthe electrondischarge device is interconnected with ,the tuned GircuitZ, 83'. The anode|4| of the -device |40 is. coupled througha coupling condenser |42 to theungrounded termif nal of the tuned .circuit Il), yandthe'cathode |43 is connected through a resistance 4|fl4 ,.in shunt to4 abypassing condenser. 1.45, t`o 'groliridi thereby beingcoupledto thegrounded terminal of the tuned circuitl. Voltage betweenthe` terminals 'ofthe tuned .circuit lllftherefore appearsbetween the anode 4| and the/cathode -,|43,1 11e.v device A|45 being arranged to transmita leadingfcurrent through its anode-and cathode.: ij 'L The anode. |4| of thedevice 40.s,supplied with operating current ,through a choke vcoil lMB and a resistance. |61 fromgthepositive terminal of ther source 22.. The screen electrode|.481 ofthe device |40 is. connected through a ,resistance 4|5|J to this vpositive jterminal, and isy bypassednto groundA through a bypassing condenser 49.

A suitable phase shifting network appliesan alternating potentialfto the control electrode |52 ofthe device |43, which potential is .leading with respect to the. alternating, voltage 4betweenthe anode |4|land the cathode |43.y Thisnetwork comprises l a series combination of a condenser ,|'5I and a vrresistance |53` connected 'in-shunt to the tuned circuit I5. Ihecontrol electrode 52 isv connected to a pointrbetween the condenser |,5I and the resistance |53, Alternating voltage between the terminals of the tuned circuitl I0 appears across the series 4combination 'of condenser |5| and resistance |53, and produces a leading current owing therethrough. This lead.- ingcurrent produces ar leading voltage across the resistance |53, which leading Voltageappears between -the control electrode |52 and the ycathode |43. The leadingvr voltage on the control elec.- trode |52 in turnallows a current to iiow between the anode |4| and the cathode |43, which vcurrent is leading with respectto the voltage across the terminals of the tunedcircuit I0.

Since the discharge device |40 transmitslleading current between its anode |4I and cathode |43 it simulates a condenser, connected in shunt tothetuned'circuit III,` so `that the tuned circuit resonates at a lower frequency. Adjustment of thefaverageevoltage across theresistance |53 d etermines Athe amount of alternating current flowing through the device |'4|l,'and, inturn detenmines the apparent size of the condenser which is simulated, so that the resonantfrequency of the tuned circuit w is thereby adjusted.Y In the upward position of the switch 41,] signals from the microphone 42, amplified through theamplifier 43 and. transmitted Lthrough the transformer l44, areimpressed, through the switch' blades 45 and 46, between ground and a conductor |54which is connected to thecontrol electrode 152. The amount of leading alternating of'. constant. frequency. SinceVA the direction of transmissiom of radiation from the antenna I3 issadiustedein accordance with the intensity` of oscillationsin the tunedcrcuit 82, 33,- the variation. of the V`direction of transmission takesplace cyclically at aconstant frequency. Y l'l'.'hemeansvby which theaudio, signals from the-.microphone 42 aref caused .to vary the fre .l quency .of oscillations. in, the tunedcircuit I0 comprises anelectrondischarge deviceMD, which K odev |43 ofthe device .|40 is therefore adjusted in response to the intensity of signals from the microphone 42, whereby the frequency of oscilla-r tions from the tuned circuit ID, and consequently the frequency .of radiation from the antenna. I3, is adjusted inresponseto the `intensity cf such signals. e 1

As mentioned previously, the transmitter, when so connected, cyclicallyvaries the directionpf radiation from theantenna |3 up and down in a vertical 'plane .atV a constant frequency, and varies the frequency of such radiation in response 'to the intensity ofsignals from the microphone 42j l directional" characteristic fof the 'jradlatio it istL emmen characterise ef-alienati my invention Pthat the intensity'crtne -raciiaicticarrier 'waive is preferably maintainediconstant, while, signals Aare transmittedfb .variation v Qfa uch f as' variation-of the direction of propagation Qtay 4loeam,. or variation of the axisofpolarization of .the'radiatim By maintaining'iheicrrienwave yintensity constant, it is assured thatamaxlmilmf amount of `r.'fx, diatjion isA received at'the'receiverzat from thejrmicrobhO-ne- 1|'66impresses'an increasfingly' positive `potential `acrossv'ooncfoi! vthe Af'x'e- As istancesfl6,il' and |18, while impressing an'in-v l1 rcreasinglynegative potential across V.the other of thersistances:` Such potentials, incre'esingin 1 @opposite polarity; make one of the 'electron-ms# :charge devices andv'l lijmorclconductle,

Y while' making Y the; athen-device A'lesamurine/tive.

all' timesfThe vagaries` of reilectionfffromgthe 1 `upper Vstrata. of the atmosphere producela minimum correspondenceheftween variations,Y of the reflection coeflicientand 'variationgof the intensity of. the VVradiation with resulting distortion ofsignal, when-such signals ,arel'transxnitted1by`vari-4 ation fof .a directional characteristic ofthe wave 'rather than'variation of its intensity.; The lirn-y n iter device illustrated injl'fig, 3 is lusefuliri [aidiing in the ,reduction of variation. er intensity of y from the upperatmosphere.; l

.1 In Fig. 4, there is illustrated@ transmit` Vsponse to a function yor* vthe intensity of "asignal, In this ligure, withv switch |63, AWhich',corresponds received signals jdue to s uchi` varying reflection ter which alters the axis lcfibplarizetidni of radis: t tion betweenovertlcaloand horizontal planes inercialternatelyV conductive in response ,tof the 'i 'fl tenSty ofisigna'ls ffrorn agrnicrophonell.

l Oscillatiorisy from the cari-ien wave generator |61 tothe controlcircuit of the discharge'devilce |.6|whichf circuitfmaf,7 be traced fron'iithe 'cone trolelectrode |66 through the tuned, secondary 'of the transformer 61,a/.resistance |69in `shunt to'v a "bypassing, condenser `|10,jla.nd ya source .|1|

oi hias'potentialrto the' cathode K12 foto.' the ide-Yl vice "l-` Theoutputciircuit ottone ,device :|61

may betrac'edjrom the, anode'fiffl'ithrough" a -iiiim'ecl ltran.siormer |714 which is coupledwtothe Consequently, oscillations frorn the generator i6,0` lare ,transferred to the exiteru'iaev |63 andiiiljin relative amountsj. which' are Jvaried fin response to theY intensityr of signals :from the AnyA receiversuitable for receiving amplitude lmodulated waveswmay beused Withthe 'transmitter, er Fig. l4, when switch" mais .in thepcsiytion illustrated, 'ifl .the accompanying antenna is more effective toj receive waves of one' polarization than of another, kwsuchianantennn lmay conveniently he vrormed,vgforr examplez by t ,o

Straightjconductor.: o Vj Apparatus is' provided in the transmitter' of Figi: ijsofthatv itsjoperation may `be Yalteredjin three ways k,similarly to the three citemative 'ways of operation .ofthe Ytransmitter of'FigLL As de- .scribed above, the operation oi' transmitter cf Fig. o 4 with'y switch ,irai in: the 5center `position isv analogous to ltheop'er'atio'n o1' "the transmitter er Fig'. 1L witnthelswitcnu in theKeent/eif.,inicieV tion., Sio arranged, thel transmitter of 158.11

jvar'ies thev radiated nea'ind1rectien,fwnnepthe .transmitter vofV Fig.' 4 varies therplane vof polarf ization of the radiated wave, in accordance with rthe intensity of the'modulating signal.Y T o prol `duce thisV eiect infthe transmitter Voi'A .l-the n,

modulating'signalsare impressed-across the re- `Militare transmitted through a k,tunedtr,ansffohrlinger ysistance 3%,.which'corresponds tojthe-,esist'ances I |69 and| 18, `'across which vthe modulstingignalsfin` therftransmitterot-rFig. 4 are-impressed;

The carmen wcyfein' the. transmitter or 'i is impressed directly on the dipoletantenna i fromV thejhigh frequency :carrier transmitter-H;

antenna |63, and a source|159! operatinglpof tential to the cathode |12.

oscillations from the'vcarrie'r lwavenlenerator are similarly transferredto the inputcircuit of the, discharge device'` |62l kthrough a V tuned `tical apparatus, to which identical ,reference transformer |16.A` The input circuitv'ofrthedei vicev |62I may betraced fromvthe control electrode f 1|11 through the secondarydor `the,tufnedl"transjl-' r,traced `from the anode |81 through Ja tuned trans'- yformer Izwhichis coupled to, the Aantenna "|64,v and the source |15, oi' potential .to .the 'cathode latine signalen the i'requencjmodulator includ-- Signals from th'ffmicrophone 66 aref-ambi# ed through the audio amplifier |65', Whosleoutl put isinbalanced, orpush-pull, relatio.and

are applied across the resistancesl |69 and |1`8fin series.` The condensers'i10 and,`|10"havel"l.`low vreactanlce at the -frequency of ,voscill'ations from n lating signals 4from the'arnpliilerm.' 1

thegenerator v |60,1butfnhave substantial reactance at the 'highest frequency of l signals Vfrom the lili-` cr'ophone |66. 'An increasingly" intense signal while in thetransmitter .of Flg..4',g suchl f transformersqllfand |16. f i o A sexplained previusly, thetransmitter of Fis. ,ltmay'befoperated lwith the switch l1 in its-'lower wave AisV impressed-across -the primaries of positiomso that the frequency ofthel carrier wave is maintained constant, while the directionof the radiated beam isevaried cyclicallyV at afre-l quency.,\1vhich` is modulated rfrom l a meanv value inaccordance with the modulating signal@ idennumbers vhave bcenapplied, is provided -infthe tran'smitterv of; 'Figy-ijior producing 'analogous re.-v sults when the switchqrl is movedto kits'ietirlandposition."-v I`n thisr positionv of theswitcl'iV |63, thecarrier"waver generatoi impresses awave oi'l constant frequencyonthe of transformers |61 7'and |16; while swce'nolr-4 curator which includes the discharge device impresses a wave throughthemagnetically-coupied ecus' sz'cnd al unen the rceietcncec wenn m.y The cudiejcmpiifier les cinena-v ing the'5di'scharge device, which. modulatesthe `frequency r`oi' the. wavesgproduced sweep escmatcr including device alf rrinfaanean lnlaccordanc'e -with the intensityofthem'iodu i With such connectlonawhichfare substantially thesame as those illustrated Y ot Fig. 1, the planeet polarizationv of the radiatedv wave (rather "than the'A direction lof the' props# :2,3345011 gatedlbearnl 1, islvaried at a frequency which v is modulated from' a mean value in accordance with `-`tlie-intensityoff` `the' modulating signal.

j {lili/hen the Aswitch |83v isin itsI right-hand.- position; corresponding vto-'th'eupperposition of the^switch 41'! of the transmitter of Fig. l, the

frequency ofL the Wave=produoedvbyf the sweep osright-handfposition of the switch |33, the modu- 'lat'ingsignal fromfthe amplifier |65 i's 'transmitte@through conductor |54 tothe high frequency-'oscillator and frequency modulator in# fcludingftlie'discharge device 140, which acts to generate' affrequencyf modulated carrier wave,

I ['Wlichis amplified throughthe'high-frequency carrier transmitter |'2f'an`d` impressed across the primaries-of thet'ransiormers |61 (and |16. Inzthis latter right-hand positionof the switch 1183; therefore, the planeof polarization of' the lwave, rathery tharithe-direction of propagation 'of the beam, is varied cyclically at a constant. yrate, :While the frequency *ofthe transmitted carrier wave is modulated in 'accordance'withthe maulatmgsignais frommeamplifier` les.

It is thus possiblel witneitherofthe transmitg ,ters of Fig. `'1 or L'Figlito modulate inth'ree diivrerentwaysa.directional'characteristic of a r'adi- 'a'tedlcarrierv wave, namely, either the direction of propagation of' the beam-orthe rv'plane of `polar` izationthereo In a first Way afdirectional charvacteri'sti'c4ofv the'radiatedwave is Vmodulated directly in'response to the intensity'offthe modul V{l'atingsignal.l lna'seoondfway yafdirectional char- :acte'ristoris modulated cyclically aty aconstant rate, Lwhile th'e frequency vof the carrier wave is modulatedlin accordance with the' modulating signals.V Inathird way' afdir'ecti-onal `cl'iaracterv'isti'c of Ythe l carrierwave isl modulated' cyclically at a frequency which-is Tin'y turn 'modulated' in responseto` the intensity of` the modulating signal.

l' Thefreceiver ofv Fig.'3 with an antenna which :is 1primarily'-l 'responsive to waves polarized in a `particular direction is suitable 'for receiving a signal from the transmitter of Fig. 4 with the v'switch 183 in the left-hand'A position. With the l fswitchsin'the'center position, as stated above,

anyreceiverfor amplitudemodulat'ed' waves havq l 'ing' an: antenna lprim arily' responsive to carrier vwawes'polarized1in one particular plane may be used'.-` W ith'y thelswitch |83 inf th'e right-hand position, a receiverf'or frequency'modulated waves maybelusedfwith'suchan antenna.

It is lto be understood that it is within the scope of myinvention to utilize modulation of more than one directional characteristic of the radiated Wave, as,for example, to utilize modulation of a beam in both vertical and horizontal planes `concurrently with modulation of the axis of polarization of the beam. Also, the amplitude or frequency of the carrier wave, if desired, may be modulated concurrently with modulation of any directional characteristic of the radiated Wave, although it is preferred to maintain the amplitudecf the wave constant.

While I have shown and described particular embodiments of my invention, it will be obvious kto those skilled in the art that changes and modfications may be made without departing from my invention in its broader aspects, and I, there- 'highest frequency of said signal, means `for fore, vaim inthe appended'claimsftofcoverr all suchchanges' and* modications as fall within the true' spiritand'- scope ofi my invention: l Wfhat Iclaim-asnewanddesire to secure by Letters Patent of 'the United States is:

1.v In combination, 'a' radio transmitter, a `radio receiver, `said transmitter and receiver-being so spacedvthat Waves vfrom said-'transmitter arrive =at said receiver principally by reason of reflection from the-higher strata of the atmosphere, means to radiate from said transmitter a Wave of constant intensity and to modulate the direction of propagation of said wave fat'affrequency modulated Yin response to a desired signal,y saidv freouency-being' substantially higher than thelhi'ghest frequency'of said-"signal, whereby said wave appears attlie location of'said receiver With'modulations of-v intensity in accordance with a functionof said desired signal, means in said receiver vresponsive tosaid modulations of intensity for producing a Wave whose"frequency'corresponds to the frequency at Whichthe direction of propagation of :said waveis modulated, and' means responsive to frequency variations of `said"last means forreproduc'ingsaid-signall 2; "In'combin'ation, a radio transmitter; 'a radio receiver, saidreceiver being' so spaced from said 'transmitterl that waves from saidftransmitter arrive at sai'dreceiver principally by reason of reec'tion from the higher strata of'the atmosfphere,"means to radiate from said-transmitter a Vwavejof constantintensity and to' modulate Vthe plane of polarization of said -wave, at aV frequency `modulated" in response'fto a'esiredSignal, said frequency being substantially hiffgherthanV the causing'said receiver toreceive said wave in greater vintensity when-ipolarizedin one plane' than when polarized in another plane, whereby said receiver vreceivessaidwave with Ymodulations in intensity in accordance'witli'a function of said signal and Variations of reflection from said higher strata affect' the receivedfintensity in minimum amount. and means in *said*l receiverresponsive to said modulations in intensity 4for reproducing .said signal. l 3. In combination, a radio transmitter, a radio receiver, said receiver being spaced from said transmitter by'suiiicient distance that the path of transmissionv of Waves between said vtransmitter and receiver may be adversely affected by disturbances-` to which said path is subject, means to Y radiate'flrom said transmitter--a Wave having its L ,plane of polarization modulated ata 4frequency "modulated, in response .to-a desired signal, said frequency Abeing"v substantially `rhigher than the highest frequency ,ofy said` signal, means-for causing said receiver't'o respond predominantly to said wave when polarized in a particular plane, Whereby amplitude modulations of said Wavecaused by said disturbances produce minimum effect on said receiver and said receiver receives said wave with modulations of intensity in accordance with a function of said signal, and means in said receiver responsive to said modulations of intensity for reproducing said signal.

4. In a signal transmission system, a signal source, means for radiating a carrier wave, means for modulating the axis of polarization of said carrier Wave at a frequency modulated in accordance with the intensity of said signal, and means responsive to modulations of the axis of polarization of said wave to receive said wave and reproduce said signal.

'1. 5.-v In a; signal transmissionsystem l. a A:signal source, means for,y radiating a carrier vvave,means for cyclically'fvarying a directionalcharacteristic of said Wave at a predetermined frequency, means y vresponsi-ve:to the intensity ofa'signal from said source for varying the frequency of `cyclic variation .of said' characteristic; and Vmeans responsive Vto'variationof tliefrequency of 1cyclic variation-of f. the 'directional characteristic ofv said-wavefto receive said-.wave and reproduce said signaL 61; In a signalqtransmisson system, aradio receiver, *comprisingl meansy toj receive @carrier Wave at different intensities as a cyclicallyvvary'- .ing directional; characteristic; thereof `varies,k the frequencyI of variation-'of said-rcharacteristic`l varying from a predetermined frequency in ac` cordancewith the intensity-.decia signal, means' vfor detecting said received car-rierwave to produce a voltage of which theintensityfvariesat a frequency corresponding -to the frequency at `.which said directional characteristcvares, and -means responsive to valfiationsof the frequency: of said Y reproducesaidfsignaL oltage: from said predetermined A'frequency to '7. *In a signalv transmission :jsystemg-afradio receiver arranged to respondtoi a-beam ofradio Waves v` Vsweeping d, past said receiverf'periodically,

- whereby said'wavesarvev receivedI by said receiver withmodulations of intensity, .thegfrequency ofv f sweep of said waves past said receiver varying from;;a predetermined .frequency in accordance. Y

receiver for'detectingasaid waves to produce aj.-

voltageofvwhich the intensity varies at a frequency corresponding to.the frequencyl of sweep ofsaid Waves, andY means .responsive to variation j of the 4frequency of saidvo1tage from `said' pref` determinedA frequencyuto reproduceY said signal.

,In a signal ltransmissior'i system, a; 'radio re-' 410 ceiver arranged to respond tofpolarized radio waves impinging on said receiver withva varying axis of, polarization, the. frequencyl of .var-iationof saidaxis varyingy frorna predetermined frequency in accordance. With .tiie.intensityof a signal,

means responsive'toyariation of the axisof polarization of said waves for receiving saidwavesat asseoir wave. cyclically .at atpredtermined frequency.. means .responsive to theintensityof a signal from said sourcel for modulating thefrequency vof .cyclic variationof said directional characteri sticfar receiver locatediat a. positionV with respect to saidradiating means Lwhe're said Y carrier. wave affects said receiver, means in said receiver for producing a wave'whose frequency correspondsfto the tre.-

`quency. of said cyclicf variation, and means for reproducingl said signal.

sponsive to frequency variationsof said glastwaye v10, In asignal ,transmission transmitter comprising `a carrier-,wave Isource. a signal source; an antenna energizedfrom-snid carrier wave. source and arranged to radiate 1a .carrier wave fromfs'aid-source, means for reectingtlie `radiated carrierrwave in different directions,- Vand means for adjustingfrsaid reecting `means to alter the direction of refiection'of carrierfwave cyclllyat affrequency modulated Y yin accordance with' a function of the intensity 'of Y a signal fromsaid signal source.- f Y 11.y In combination, a radiator, a reflector arranged to adjust thedirection of propagation of wav'es radiated by said radatorrin acvzeordxainoeVNV Y ywith kthe tuning thereof, means` responsive `*to `Wavesreceivedlcy,said reector fromsaidradiator foriadjustingsaid tuning, a signalsourcerand means to.` adjustfsaid last means to vary said tuning in responsev to signals, from 'saideour; f '-.Y fl z 12..-,In combination, afhalf wave dipole radin#v tor, a, dipole reiiector arranged parallel. to said radiator'to adjust theV direction of .propagation o! waves radiatedfrom said radiatorin accordance .with the tuning ,gthereofy means'icomprising a v'series resonant-circuit connected v .ratedhalves of said reector to adjustfthertunim thereof,- andmeans to adjust theresonant quency of saidlresonant circuit with lt0 the r `frequency' of said waves tovarythetuning of said y reiiector in response (to signals to. be transmitted.

- 13. Ina signal transmissionfsystem, animal different intensities asv said v.axis ofpolarization I .variesgymeansin said-receiverfor detecting: said received Waves to produceavoltage of whichvthe intensity varies at a frequencyk corresponding 'to .A

the frequency .at whichv said, axis varies, and means responsive to'variationfof the frequency of saidvcltage from said predetermined` frequency t reproduce said signal, l v' source,v means for' ra'diatingyfa carrier Wavefof a predetermined frequ'ericy,` meansjforf varying a directional characteristic fof said radiated carrier f f :55y -9.'In a signal' ransmission; system, asignal function of; the intensity of ausignalltrom said signaljsource for modulating the frequ vencysofone Vof saidwaves.; Y, v I

14; vIn a signal transmissionsystemra source, means for radiating aqcarrier wave', means for cyclically varying the plane, of polarization'of said wave at `a .predetermined "frequency,

means responsive to the intensity .of 'a .signalffrem said source for vvaryin'gth'e .frequency of cyclic variation of saidplane of polarization; 1 1, 

